Versatile Friedel-Crafts-type alkylation of benzene derivatives using a molybdenum complex/ortho-chloranil catalytic system.
A variety of molybdenum complexes catalyze Friedel-Crafts-type alkylation reactions of benzene derivatives with alkenes and alcohols in the presence of an organic oxidant, o-chloranil. The utilization of [Mo(CO)(6)] and two equivalents of o-chloranil catalytically furnished the hydroarylation product of norbornene with p-xylene at 80 degrees C, whereas [Cr(CO)(6)] and [W(CO)(6)] failed to catalyze the same reaction, thus indicating the importance of the molybdenum source. The best results were obtained when a molybdenum(II) complex [CpMoCl(CO)(3)] (Cp=cyclopentadienyl) was used as a precatalyst. The hydroarylation reactions also took place with styrenes, cyclohexenes, and 1-hexene as olefin substrates. The electrophilic-substitution mechanism was proposed on the basis of the ortho/para selectivities and the Markovnikov selectivities observed for the hydroarylation products. Our hypothesis was further corroborated by the fact that in the presence of the [CpMoCl(CO)(3)]/o-chloranil catalytic system, secondary, benzylic, or allylic alcohols participated in the alkylation of benzenes with similar selectivities.
Yamamoto
Yoshihiko
Y
Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan. omyy@apc.titech.ac.jp
Itonaga
Kouhei
K
D000438:Alcohols / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry; D000478:Alkylation; D001555:Benzene Derivatives / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D002703:Chloranil / Q000031:analogs & derivatives* / Q000737:chemistry; D008872:Microwaves; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D013237:Stereoisomerism
D000438:Alcohols; D000475:Alkenes; D001555:Benzene Derivatives; D009942:Organometallic Compounds; D016877:Oxidants; D002703:Chloranil; D008982:Molybdenum; C039499:2-chloranil